*******Note that forecast and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********
...SATURDAY OCTOBER 1 2022 7:25 AM EDT...
Ian has lost its tropical characteristics and is now a remnant low centered over north-central North Carolina... see remnants of Ian section below for more information. Elsewhere... monitoring the following areas for signs of development:
(1) See area of interest #34 section below for an update on the tropical wave of low pressure in eastern tropical Atlantic that continues to be monitored for signs of development.
(2) The tropical wave of low pressure that was previously over central Africa is now over western Africa while making westward progress. Computer model support showing this wave developing is currently not present... and area of interest #34 to the west is expected to slow down while interacting with an upper trough to move southeast into the region. This could ultimately result in this tropical wave catching up to and then merging with area of interest #34 instead of developing on its own as a separate entity.
(3) The tropical wave of low pressure at 39.5W longitude is currently inactive and is expected to continue west into the eastern Caribbean Sea in about five days. Meanwhile split flow upper divergence over the eastern Caribbean could increase during that timeframe... between a remnant upper vortex to the northeast associated with the currently decaying string of central Atlantic upper vorticity and southeast side of an upper ridge axis to persist over the northwestern Caribbean Sea. This tropical wave could see an increase in thunderstorm activity due to this upper divergence... therefore this tropical wave may require monitoring for development in the Caribbean in the days ahead.
New to this site this year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development. In this scheme... will reset back to #1 at the start of next year (January 2023). The current area of interest in this blog post is designated #34 as the other numbers were used in previous birdseye view posts. This scheme is to reduce confusion as Atlantic tropical activity increases during the peak of the hurricane season... when multiple simultaneous areas of interest begin and end which previously required shuffling around the area of interest numbers from update to update.
REMNANTS OF IAN... Special update #116A available on the home page of this site chronicles the landfall of Hurricane Ian across the Carolinas on Friday. Since 5 PM EDT on Friday Ian was downgraded to an inland remnant non-tropical low pressure area supported by the eastern divergence zone of the upper trough that has been to Ian's immediate west. A southward-digging upper trough from eastern Canada will merge with the upper trough to Ian's immediate west in the next 24 hours...resulting in a complex upper trough. The divergence zone of the complex upper trough is expected to be quiet elongated... resulting in a broad frontal low pressure area where Ian is expected to loses its identity within over the next day or so. Based on the latest wind observations at National Weather Service stations... the remainder of the gusty winds over southeastern Virginia that were caused by the pressure gradient between Ian's northeast side and south side of surface high pressure ridging to the north have diminished as Ian continues to weaken... and the associated coastal surf will also follow suit as we progress through today. Coastal surf further north... along the coastal northeastern United States... will be associated with the onshore wind flow caused by the strong surface ridging to the north instead of Ian. Doppler radar as of this writing shows the remainder of the rainfall is currently located across West Virginia... Pennsylvania... New Jersey... Massachusetts... Connecticut... and Rhode Island. Isolated flash flooding cannot be ruled out in this region. This is my final statement on Ian on this blog as it is no longer a tropical system.
AREA OF INTEREST #34...The tropical wave of low pressure currently in the eastern tropical Atlantic in recent satellite frames is displaying a better defined area of rotation near 9.5N-24W... with associated skeletal curved banding in the showers and thunderstorms. This indicates the tropical wave is consolidating further west... away from a pocket of low surface pressure being generated over northwestern Africa by the eastern divergence zone of an upper vortex. Therefore over the next 48 hours this system should continue west around the south side of the steering Atlantic surface ridge... and the updated forecast track shown in the outlook below is adjusted westward. I have raised my short-term odds of tropical cyclone formation to 30% as the tropical wave is developing a better defined area of rotation as noted above.
In the longer range a chunk of the current northern Atlantic upper trough will slide southeast into the environment of this system due to the strength of a warm upper ridge currently building in the western Atlantic (this upper ridge was initially bolstered by warm surface southerly flow ahead of Ian... and will continue to be bolstered by warm southerly surface flow ahead of a broad frontal low pressure area that will materialize with the aid of the complex upper trough to absorb Ian's remnant system). Models currently agree that the eastern divergence zone of the approaching upper trough fragment will weaken the south side of the steering Atlantic surface ridge to allow this system to float more northward in track by 72+ hours. This tropical wave also has potential to evolve into a more complex disturbance in the 48 to 72 hour window while transitioning into a broadening disturbance supported by the sprawling eastern divergence zone of the upper trough fragment... while potentially absorbing an adjacent tropical wave coming in from the east (note this adjacent wave is currently observed with a distinct area of thunderstorms over western Africa). I do not raise odds of development above 30% in the 48 to 72 hour window due to southwesterly shear to be induced by the cut-off upper trough and the potential for the disturbance to lose organization while broadening. At 96+ hours I climb development odds to 50% as the cool core upper trough fragment and associated shear begins to weaken while it remains cut-off from high-latitude cold air... and more time will have elapsed to allow for the broadening disturbance to re-consolidate. The long range support in the models... which still currently agree on eventually developing this system into a tropical cyclone... also encourages the higher odds by day 5. However my 50% odds are a notch lower than the NHC's current 70% due to the aforementioned unfavorable factors this disturbance could encounter in the 48 to 72 hour window.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0600Z Oct 2)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 9.8N-28W)
IOH 48 Hr Outlook (0600Z Oct 3)...30% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-32W)
IOH 72 Hr Outlook (0600Z Oct 4)...30% chance of tropical cyclone formation (eastern tropical Atlantic near 12.5N-33W)
IOH 96 Hr Outlook (0600Z Oct 5)...40% chance of tropical cyclone formation (eastern tropical Atlantic near 14.5N-34W)
IOH 120 Hr Outlook (0600Z Oct 6)...50% chance of tropical cyclone formation (eastern tropical Atlanic near 17N-36W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
0000Z (Oct 1) CMC Model Run...
**For area of interest #34... tropical cyclone formation suggested near 13.5N-30.5W at 90 hours... curves increasingly north in track and reaches 17N-32W at 126 hours as a compact top-end tropical storm.
**Tropical wave currently at 39.5W longitude begins to amplify (strengthen) in the western Caribbean Sea to the southwest of Jamaica and along 80W longitude at 168 hours.
0000Z (Oct 1) ECMWF Model Run...
**For area of interest #34... tropical cyclone formation suggested near 17.5N-32.5W at 120 hours.
0000Z (Oct 1) GFS Model Run...
**For area of interest #34... tropical cyclone formation suggested near 15N-29.5W at 105 hours... curves increasingly north in track and reaches 17.5N-31W at 120 hours as a compact top-end tropical storm.
0000Z (Oct 1) NAVGEM Model Run...
**For area of interest #34... tropical wave becomes a tropical low south-southwest of the Republic of Cabo Verde Islands at 12.5N-25.5W at 66 hours... tropical low moves west-northwest and reaches 14.5N-33.5W at 120 hours.